Thyroid UK
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Help with test results

Morning all, I am a new member to this forum and would really appreciate any help or advice in relation to my test results. I was due to have cosmetic surgery last week which has since been postponed due to my blood results being too high;

Tsh 1.49 (0.27-4.2)

Free Thyroxine 33.4 (12.0-22.0)

I have been taking 175mcg for years and was recently told to increase to 200mcg. I started to loose weight quickly and experienced palpitations, my nurse then reduced me back to 175mcg to reduce my Free Thyroxine. Does this sound right? I am sure my doctor doesn't have a clue when it comes to hypothyroid patients! My next question is how long will it take to reduce as they wont operate until my levels are stable? Many thanks in advance for any advice! X

7 Replies

Did you take levo before your blood test?


Yes? I've heard conflicting reports some say I should, others say not to? 😩


I believe that's why your test is 'out'. It is best to leave 24 hours between levo and the blood test. Usually the earliest appointment is best. Maybe have another blood test in a couple of weeks when you've been on your reduced dose of 175mcg.


Your TSH is ridiculously high for your FT4. That is, with an FT4 that is around 50% higher than the top of the range, we would usually expect TSH to at least be below range, and quite possibly at the very bottom.

I very much agree with shaws. This would very likely be due to taking levothyroxine a relatively short time before your blood draw. Long enough for the "bow wave" of the dose to have raised your FT4. But TSH usually changes more slowly - so it does not catch up with the peak FT4. (One of the claimed advantages of TSH for initial and ongoing testing is that it tends to reflect the average thyroid hormone levels. In this case, that might have been an advantage in making it clear that the FT4 needs to be questioned. TSH test alone would have left you looking fine or even very slightly under-dosed.)

If that FT4 result is not due to taking your medication before the blood draw, then someone would need to look further in an attempt to explain the discord between the two test results.

[It would be expected that FT4 peak around two hours after taking the dose. FT4 then slowly tails away over the next few hours.]


Thank you both so much for your advice. I have my next blood test on 2nd April at 3pm so am best to leave taking the 175 that morning and taking it after my test?


The time 3p.m. isn't so good due to the fact that the TSH changes throughout the day, being highest early a.m. and GP might reduce levo due to the TSH being low/very low later in the day. Adjusting doses of levo unnecessarily so can lead to problems for the patient.

As you know we take levo first thing with one glass of water, then you miss this dose for the blood test. If you've eaten you have to leave 2 hours minimum either side of taking levo when you have a blood test.

If you take levo at bedtime (as some do) you also have to have an empty stomach and miss this dose if you have blood test next day.


1) Always get the earliest appointment possible for getting blood drawn for a thyroid blood test. Between 7am - 9am is best. If you get tested later than this your TSH will be lower. Many doctors will reduce medication on the basis of a low TSH and most of us don't want this to happen.

2) Do not eat or drink for 10 - 12 hours before the test, except for plain water. Apparently TSH lowers after eating.

3) If you usually take your levothyroxine in the morning, don't take it on the morning of the test until after the blood draw. Instead, take it immediately after the blood draw.

4) If you usually take your levothyroxine at night, the day before the test don't take any levothyroxine at all. On the day of the test take two doses - one immediately after the blood draw, and the other at night as usual.

5) Stick to these conditions every single time you get your thyroid tested. It will reduce the risk of you getting inappropriate cuts to your medication. It also means that your tests can be sensibly compared from one time to the next to see if something is changing that you need to know about.


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